I'm having the exact same problem. And it also happens with Facebook for me, and only with Facebook. I'm using IE 7, and if I have FB open in a tab and then close the tab, I get an endless stream of new brower windows opening to the FB page I was just on. I've run scans, and I have no viruses. Like I say, it only happens in Facebook, and only if I've got Facebook open in a tab, not if it's the only tab in the window (if that makes sense).